The present invention relates to rotational electric machines and, more particularly, to a multi-piece two-pole generator rotor including flat for machine fields.
In electric machines having a rotor and a stator, the rotor is provided with field windings, and the stator is provided with armature windings. The rotor is typically provided with rotor spindles to effect rotation. With this structure, however, the spindles on each end of the rotor body require the ends of the field winding to be formed into an arc concentric with the spindle. See, e.g., FIG. 1. This rotor construction including a one-piece rotor forging and end winding modules having curved ends is described in co-pending U.S. patent application Ser. No. 09/491,504, filed Jan. 26, 2000.
It is desirable to flatten the winding construction of the prior end winding modules and eliminate the arcs required for concentricity with the spindle. A flattened winding construction is described in U.S. Pat. No. 6,437,476. Flat windings with straight end turns extending diametrically across the rotor, however, are susceptible to elongation under the pull of centrifugal forces. The introduction of a predetermined axial offset can allow the end arms to lengthen and shorten with changes in rotor speed, without suffering elongation. On the other hand, the unsupported end arm will be subject to minimum induced centrifugal forces and effect support from the straight section of the winding.